Polystyrene-type resins plasticized with high boiling fatty acid alkyl esters



. substantiaily greaterlthan that of ortho Patented Dec. 24, I946 POLYS'I'YRENE-TYPE RESINS PLAS'IICIZI'JD WITH HIGH BOILING FATTY ESTERS ACID ALKYL Frank J. Soday, Swarthmore, Pa., assignor to The United Gas Improvement Company, a corporation of Pennsylvania No Drawing. Application July 7, 1942,

Serial No. 450,083

11 Claims.

This invention relates to new compositions of matter comprising polystyrene-type resins and certain high-boiling esters.

More particularly, this invention pertains to resinous compositions comprising one or more resins derived by the polymerization or copolymerization of one or more compounds selected from a list comprising styrene and substituted styrene and at least one plasticizing agent selected from a list comprising certain esters containing from 19 to 33 carbon atoms.

An object of the invention is to provide resinous compositions which have been plasticized sufficiently to impart a substantial degree of flexibility thereto. Another object of the invention is the provision of molding compositions possessing improved flowing properties at elevated temperatures. A further object of the invention is the provision of a casting composition comprising monomeric and/or partially polymerized styrene and/or substituted styrene containing one or more esters of the type described adapted for the production of castings or other formed objects, particularly objects containing metallic or other, inserts. Other objects and advantages of the invention will be apparent to those skilled in the art upon an inspection of the specification and claims.

Styrene, or substituted styrenes conforming to the following formula l in which a, b, and c'each may represent hydrogen, halogen, or alkyl, cl may be halogen or alkyl, and 11. may beany integer from to '5, may be polymerized to form light-colored, or colorless, resins possessing excellent physical properties.

Examples of substituted styrenes which are particularly well adapted to the production of resins of this type are the nuclear substituted methyl styrenes, such as m-methyl styrene, p-

methyl styrene, and o-methyl styrene.

Particularly desirable resins are obtanied by the copolymerization of mixtures of meta methyl styrene, para. methyl styrene, and ortho methyl styrene in which meta methyl styrene and para methyl styrene are each present in proportions methyl (c1. zen-ac) styrene. Excellent results are obtained when the preponderating unsaturated hydrocarbon present in the mixture to be polymerized is meta methyl styrene, followed by para methyl styrene and ortho methyl styrene, in.the order given. Good results may be obtained when the preponderating unsaturated hydrocarbon present is para methyl styrene, followed by meta methyl styrene and ortho methyl styrene in the order given.

Copolymers possessing excellent surface hardness characteristics, as well as other desirable properties, maybe prepared by the polymerization of a mixture of nuclear-substituted methyl styrenes containing from 55 to 75% meta methyl styrene, from to 45% para methyl styrene, and from 1 to 10% ortho methyl styrene.

Polymers possessing unusually good physical properties also may be obtained by the copolymerization of styrene with one or more substituted styrenes, such as the nuclear-substituted methyl styrenes.

Resinous materials possessing very desirous properties may be obtained by mixing polystyrene with one or more polymers obtained from substituted styrenes, such as the nuclear-substituted styrenes. Substituted styrene polymers obtained by the polymerization of a mixture of meta, para, and ortho methyl styrenes, in which the meta isomer predominates, are preferred.

For many uses, however, Ihave found that the foregoing resins do not possess satisfactory elas-' tic characteristics.

Thus, for example, the use of polystyrene, polymethylstyrene, styrene-methyl styrene copoly- 5 mers, and/or polystyrene polymethylstyrene mixtures for the preparation of castings or molded objects containing metallic, or other, inserts, has given unsatisfactory results in certain cases. Thus, for example, the molding or casting may 40 develop cracks around the metallic insert, resulting in a definite reduction in the mechanical strength, and other properties, of the unit.

This is particularly undesirable in thecase of certain electrical units, such as condensers, conductors, and the like, where the formation of cracks in the cast or molded object may result in undesirable electrical phenomena, such as corona discharges. In the case of radio and television condensers imbedded in polystyrene or'polystyrene-type plastics, the formation of corona discharges in cracks formed in the plastic mass largely interferes with theoperation of the unit, and may render it entirely unsuited for this type or work.

In addition, the formation of cracks in the plastic mass in which condensers, or similar units, are imbedded may permit moisture to penetrate the unit, thus impairing its emciency and rendering it unsuited for certain applications.

I have discovered that the formation of cracks in polystyrene type plastics may be retarded or completely eliminated, and certain of the other physical properties of the material improved, by the incorporation therein of an ester conforming to the following formula CH3 (CH2) :COOCH: (CH2) vCH:

in which a: has a value ranging from 8 to 18 and 1! has a value ranging from 7 to 11.

Unusually desirable results are obtained when esters of the type described in which a: has a value ranging from 10 to 16 and 1 has a value ranging from 8 to 10, are employed.

Examples of esters which have been found to be particularly good plasticizing agents for polystyrene-type plastics are undecyl laurate,undecy1 myristate, and undecyl stearate.

It is to be understood, of course, that two or more esters of the type described may be employed, as well as'mixtures of one or more esters of the type described in conjunction with the use of one or more plasticizing agents of other types, such as the chlorinated diphenyls.

Any desired proportion of plasticizing agent of the type described herein may be employed, although care should be taken not to exceed the compatibility limits of the plasticizing agent, of

agents, selected and the polystyrene-type plastic. For many purposes I have found that 10%, or even less, of plasticizing agent is sufficient to impart the desired flexibility, as well as other desired properties such as freedom from cracking or checking, to the polystyrene-type plastic. Higher proportions may, of course, be used if desired.

Esters of the type conforming to the foregoing formula may be added to the plastic at any stage of its preparation, such as before, during, and/or after polymerization. Thus the ester, or mixture of esters, may be added to the monomeric styrene and/or substituted styrene prior to, or during, the polymerization thereof, leading to the production of a polymer or copolymer through which the plasticizing agent has been uniformly distributed. This is particularly desirable from the standpoint of the production of castings. Such castings may,

of course, contain metallic, or other desired in-' serts.

On the other hand, a plasticizing agent of the type described may be added to the polystyrenetype plastic at any stag subsequent to the polymerization thereof. The plasticizing agent may be added in any desired manner, such as by masticating a mixture of the plastic and plasticizing agent on hot rolls until a uniform blend has been achieved. Another method comprises the addi tion of the plasticizing agent to a solution of the plastic in a suitable solvent, followed by removing the solvent, if desired, by any suitable method. This may involve distillation, which may be assisted by the use of steam and/or reduced pressures, working on hot rolls, spray drying, and the like.

The plasticized product then may be further processed, if desired. Thus, it may be subdivided to-form a molding powder, or it may be extruded to form rods, tubes, foil, film, and other shapes.

Other ingredients also may be incorporated in the polystyrene-type plastic prior to, during. or after the addition of. plasticizing agents of the type described herein, and such' additions may 4 be made prior to, durin or after the formation of the plastic. These additional ingredients may include one or more agents selected from a list comprising dyes, pigments, fillers, other plasticizing agents, rubber, both natural and synthetic.

and other resinous and/or plastic materials.

The polymerization of the styrene or substituted styrenes employed'in the preparation of plastic compositions of the type described herein may be carried out in any desired manner, such as by the application of heat. In addition, certain catalytic agents also may be employed, either alone or in conjunction with the simultaneous, or otherwise, application of heat. Examples of suitable catalytic agents are peroxides, such as hydrogen peroxide, benzoyl peroxide, and the like, metallic halides, metallic halide-organic solvent complexes, and contact agents such as clay, nvated clay, "alumina, silica gel, an the like.

The advantages to be obtained by the use of my plasticizing agents over those used heretofore may be illustrated by the following examples.

Example 1 A mixture of 5 parts of dibutoxethyl phthalate and 95 parts of monomeric styrene was placed in a cylindrical container, after which an aluminum rod /4" in diameter and sumciently long to project above the surface of the monomeric styrene, also was placed in the container. The monomeric styrene then was polymerized by heating for 72 hours at 120 C., 48 hours at 140 C., and 20 hours at 65 C.

Upon removing the polystyrene casting containing the metallic insert from the container, and permitting it to stand overnight, definite signs of cracking were observed. The majority of these cracks originated on the surface of the metallic insert within the casting and penetrated the plastic mass for considerable distances. At the end of one week's storage, the casting was cracked to an extent suflicient to render it useless for any commercial application.

The experiment was repeated, using a number of other commercial plasticizing agents, with the following results.

In addition to cracking, the majority of the plasticized castings listed showed excessive blushing, crazing, checking, pitting, or other surface imperfections after the indicated storage periods.

The following experiments will serve to illustrate the greatly improved results to be obtained by the use of esters of the type described herein as plasticizing agents for polystyrene-type plastics.

Example 2 A casting similar to that obtained in Example 1 was prepared by the polymerization of a mixture of 5 parts of undecyl stearate and parts of monomeric styrene. I v

The plasticized casting was colorless, transauaaae t, and entirely free from surface, or other imperfections after a storage period of 39 weeks.

Example 3 This was a repetition of Example 2, with the exception that a mixture of parts of undecyl laurate and 95 parts of monomeric styrene was employed in the preparation of the casting.

, The plasticized casting was entirely free from cracking and other imperfections after a storage period of 63 weeks.

Example 4 This was a repetition of Example 2. with the exception that the casting was prepared by the polymerization of a mixture of 5 parts of undecyl myristate and 95 parts of monomeric styrene.

The plasticized casting obtained was clear and free from surface defects often a storage period of 84 weeks.

Example 5 Polystyrene plasticized by the addition of 5% undecyi stearate is molded at atemperature of 200 C. and a pressure of 2000 pounds per square inch. A colorless, clear molded object possessing excellent mechanical properties is obtained.

Example 6 Polymethyl styrene plasticized by the addition of 5% uudecyl iaurate is extruded in the form of, a rod under a pressure of 2500 pounds per square inch and a temperature of 150 C. The rod obtained possesses good surface characteristics and excellent mechanical properties.

Example 7 limited only asrequired by the prior art- I claim:

1. As a new composition of matter, a plastic composition comprising. a polymer of material selected from the group consisting of styrene and albl styrene, and a plasticizing agent conforming to the following formula CEKIHchCOOCHflCHaMCHi in which I has a value in the range of from 8to18and'yhasavalueinthe 'l to 11.

2. As a new composition of matter, a plastic composition comprising a polymer of material selected from the group consisting of styrene claims without departing from the spirit of the invention. which is intended to be 6 and alkyl styrene, and a plasticizing agent conforming to the following formula CH3(CH:) ICOOCHflCHahCH:

inwhichzhasavalueintherangeoffrom 10 to 16 and 1 has a value in the range of from 8 to 10.

3. A plastic composition comprising a polymer of material selected from the group consisting of styrene and alkyl styrene and undecyl stearate as a plasticizing agent.

4. A plastic composition comprising a polymer of material selected from the group consisting of styrene andalkyl styrene and undecyi laurate as a plasticizing agent.

5. A plastic composition comprising a polymer of material selected from the group consisting of styrene and alkyl styrene and undecyl myristate as a plasticizing agent.

6. A plastic composition comprising polystyrene and a plasticizing agent conforming to the following formula CHMCHzhCOOCHflCHa) gCHJ 7. A plastic composition comprising olymethyl- Y styrene and a plasticizing agent conforming to ran from the following formula CHMCHzhCOOCHflCHahCH:

V CHs(CH2).-:COOCH2(CH2MCH3 in which a: has a value in the range of from .10 to 16- and 1 has a value in the range of from 9. A polystyrene casting containing at least one metallic insert and a plasticizing agent corresponding to the following formula cnucmncoocnucmiycm in which a: has a value in the range of from 10 to 16 and 11 has a value in the range of from 8 to 10.

10. A polymethylstyrene casting containing at least one metallic insert and a plasticizing agent corresponding to the following formula in which a: has a value in the range of from 10 to 16 and 1: has a value in the range of from 8 to 10.

11. An electrical conductor imbedded in polystyrene containing a plasticizing agent correspending to the following formula cmpcmilcoocnucrimcm in which aims a value'in the ran e of from 10to 16 andyhasavalueintherangeoffrom 8 to 10.

FRANK J. SODAY. 

